Question

If both x and y are in quadrant IV, and sin x = -2/3 and cos y = 1/4. Find cos (x-y)

Answer 1

cosxcosy+sinxsiny

Answer 2

cos( x-y)= cos x cosy+ sinx siny

Answer 3

sin x= -2/3
cox x =sqrt(1 +4/9)=sqrt(13)/3

Answer 4

oh sorry

Answer 5

cosx = sqrt(1-4/9)= sqrt(5)/3

Answer 6

cosy =1/4
siny =- sqrt(1-1/16)=sqrt(15)/4

Answer 7

put the values in formula

Answer 8

ok thanks....another questions is to find sin (x+y) with the same variables...
can you help me get started on that one also?

Answer 9

oops, once would have been enough

Answer 10

sin(x+y)= sinxcosy-cosxsiny

Answer 11

values are same

Answer 12

thank you

Answer 13

so for cos (x-y) would it be: (√5/3)(1/4)+(-2/3)(√15/4)=(√5/12)+(-2√15/12)= √5-2√15/12

Answer 14

siny is negative in fourth quadrant
sin y =-sqrt(15)/4

Answer 15

ok so it would be √5+2√15/12

Answer 16

for sin (x+y) would it be (-2/3)(1/4)-(√5/3)((√15/4)= -2/12-√75/12=-2-5√3/12

are my negatives and positives right?

Answer 17

u again missed that siny is negative

Answer 18

-2/12+√75/12

Answer 19

for sin (x+y) would it be (-2/3)(1/4)-(√5/3)((√15/4)= -2/12-√75/12=-2-5√3/12

are my negatives and positives right?